Overview

Comprehensive Description

Description

An intertidal barnacle with six solid wall plates, an oval-shaped operculum opening, and a membranous base. Juveniles have a kite-shaped opercular opening. The rostral plate is relatively narrow, plates are of roughly equal size, and its rostral plate is not fused with the rostrolateral plates. Usually conical in shape, however when crowded may become tubular. It may reach a diameter of approximately 14 mm, depending on habitat, food availability and level on the shore. The tissue inside the opercular aperture is bright blue with black and orange markings.Before 1976 Chthamalus montagui was considered a variety of Chthamalus stellatus, but in 1976 was identified as a distinct species, due to differences in its vertical zonation on the shore and morphology, particularly in the shape of the opercular plates, setation of the smaller cirri. (Southward, 1976).

ST---AT-S-C-I---------------------------CATAAAGATATTGGAACTTTATATTTAATTTTTGGGGCATGATCTGCAATAGTGGGAACTGCTCTT---AGTTTACTGATTCGAGCTGAATTAGGACAACCTGGTAGATTAATCGGGGAT---GATCAAATCTACAATGTAATTGTAACGGCTCACGCTTTTATTATAATTTTTTTTATGGTTATACCTATTATGATTGGAGGATTTGGTAATTGATTATTACCTTTGATA---TTGGGAGCTCCTGACATAGCATTTCCTCGTTTAAATAACATAAGTTTTTGACTTCTTCCTCCTGCTTTAATACTTTTAATTAGAGGTTCACTTGTTGAAGCTGGGGCAGGGACTGGGTGAACAGTCTATCCCCCTTTGTCAAGAAATATTGCTCATTCTGGAGCTTCTGTAGATTTATCT---ATTTTTTCTTTACATCTAGCTGGTGCTTCTTCTATTTTGGGGGCAATTAATTTTATATCTACAGTAATTAATATACGAGCTGAAACTTTGACTTTTGATCGTATTCCTTTATTTGTATGAAGAGTATTTGTTACAGTAATTTTACTTCTTCTTTCTTTACCGGTGTTAGCCGGA---GCAATTACAATATTACTGACGGATCGAAATTTAAATACTTCCTTTTTTGATCCAACAGGAGGGGGTGATCCAATTCTTTATCAACATTTATTTTGA-- end --

The chalky white shell of C. stellatus has a kite-shaped opercular opening when it is a juvenile and an oval operculum opening when it is an adult. The shell is made up of six solid wall plates of approximately equal size. Its relatively narrow rostral plates remain separate from its rostrolateral plates and do not fuse. C. stellatus has bright blue tissue with black and orange markings which can be seen when its opercular aperture is not tightly closed. Depending upon environmental conditions and the amount of food available, it can reach up to 14 millimetres (0.55 in) in diameter.[4]

Like most barnacles, C. stellatus is hermaphroditic and capable of self-fertilisation when isolated, but individuals typically take on either a male or female role in order to mate. Their penises are significantly longer than their bodies and are used by the stationary "functional males" to search the area for an equally stationary "functional female" neighbour to fertilise.[5]

Barnacles of this species produce about 1,000 to 4,000 eggs per brood when functioning as female.[5] The fertilised eggs remain inside the shell of the adult until they are released as nauplii, free swimming larvae which float on currents along with other plankton. After several moults they metamorphose into a cyprid, a stage at which they cannot feed. The cyprid swims in search of a suitable surface on which to attach itself, head first, in order to metamorphose into the familiar, hard-shelled, immobile form.[4][6] The duration of its breeding season can be temperature dependent, and it produces fewer broods near the northern limit of its range.[7]